How to render Backfacing Culling
Two years late, but for reference :)

If you want to have backface culling in cycles you can use a material setup like this:



Which basically uses two materials, a diffuse one (or whichever one you want) and a transparent material (to cull backfacing surfaces). You just mix them using the backfacing output of the geometry node so that backfacing surfaces use the transparent material.